Improvement And Inspection Of A Portable Rail Measuring Meter

Rolling contact between wheel and rail transferring the power of traction and braking, results in wear. Wear is an important factor that affects the safety and economic efficiency of railway transportation. It is difficult also important to obtain curves and wear parameters of railhead accurately. In this article, studies are focused on expanding the scope of rail measuring meters, improving its accuracy and determining the method to realize traceability.Researches of rail configuration and measuring techniques show that the difficulty in the measurement of rail wear is the determination of the measuring basis. To improve the reliability of measuring basis, a method was proposed in which the jaw. of the working edge of railhead was involved, measuring basis was determined using weight coefficients, the adaptive coordinate system was established via software. The requirements of measuring scope according to the method above could not be met using existing meters. On the basis of existing studies, a new mechanism was proposed. Simulations were conducted to inspect its measuring scope and optimize the parameters. Results showed that the measuring scope of the mechanism was expanded and met the requirements.The measuring mechanism, detection portion and related algorithms were designed. Through algorithms, including positive solution, curve stitching, Gaussian filtering and two-point radius compensation, angle data obtained by sampling simulation were transformed to a measured curve. The key points on the measured curve used to determine the measuring basis were calculated. Then weight coefficients were chosen according to the designed algorithm. The rotation angle and translation needed to align the curves was calculated, ultimately, the alignment of measured curve and standard curve was realized. Several measured curves were substituted into the algorithm. The magnitude of quadratic sum of the distances (mm) between the corresponding key points of two curves was10(?) which meant the proposed method in measuring basis determination and coordinate system establishment was achieved.Analysis of the error source of the meter was carried out. Using MATLAB, principle error, single-factor error and quantization error of the encoder were simulated. Results are as follows:the magnitude of principle error is10-13mm, so that the effect on the measurement can be ignored; error caused by each factor is within±0.05mm, the error transmission factor of encoder is much larger than the others. Then the quantization error of encoder was analyzed separately, found that error at the rail head tread was beyond the design requirements. Without changing the resolution of the encoder, the comprehensive error in measuring process calculated in normal direction is within the range of (-0.02～0.015) mm. It is showed that instead of raising the resolution of encoders, reasonable filtering algorithm can improve the quantization error of encoder effectively, and the total error of the meter meets the requirement of design.By the comparison of the metrological traceability and dissemination of the value of quantity, verification and calibration, calibration was chosen for the meter to realize its traceability finally. Calibration method of the meter was designed according to JJG (railway)133-1997and JJF1071-2010. The uncertainty of calibration was assessed according to JJF1130-2005.